There are numerous patents disclosing floating docks made of modular buoyant wharf structures, frequently referred to in the art as floats and pontoons. Some of these prior art structures have been commercialized. The prior art structures, however, have had certain problems, for example, relating to cost, instability in response wave action of the body of water in which the structures are located, and relatively short useful lifetimes.
Usab, U.S. Pat. No. 3,091,203, discloses a concrete floating wharf structure including multiple modules formed as concrete shells tied together by elongated rods extending through tunnels in upper portions of the shells. The manufacture of the concrete shells is expensive, involving three different concrete pouring operations, one for the floor of the shell, a second for the shell walls, and a third for the shell roof. The concrete is poured into a mold around reinforcing mesh. A Styrofoam box goes inside the mold and includes a floor for supporting the concrete of the shell roof. Walls of the shell are formed between the Styrofoam box and the mold, which is removed after the concrete has set. The three step concrete pouring operations are expensive and some skill is required to form the concrete walls of the shell. In addition, the concrete shell is relatively brittle and the exterior surfaces thereof have a tendency to break in transportation, handling and use. In addition, special concrete must be used to prevent electrolysis action between the concrete and salt water where the modules may be located. The electrolysis action has a tendency to eat away the concrete.
Usab is the patentee of other patents having disclosures of structures similar to those found in his '203 patent. These other patents are Reissue 24,837, a reissue of U.S. Pat. No. 2,857,872, and 3,128,737.
Each of Thompson, U.S. Pat. No. 4,715,307, Shorter, Jr., U.S. Pat. No. 4,559,891, Jung, U.S. Pat. No. 4,318,362, and Finn, U.S. Pat. No. 4,947,780, discloses a buoyant modular wharf structure, a multiplicity of which are secured to each other to form floating docks. Each module includes a concrete upper portion and a buoyant lower portion made of a material other than concrete. Each of Thompson, Shorter, Jr., and Jung specifically state that the low density material in the lower portion of each module is Styrofoam. In general, the Styrofoam is packed into a shell made of an organic compound.
The structures of these patents are expensive because of the requirement, in each, for a form that must be disassembled after the concrete has been poured and set. In addition, none of these structures deal with the problem of water that has a tendency to collect in the concrete, particularly between interfaces of the concrete and other parts of the module. The collected water has a long term adverse effect on the module lifetime, particularly in climates where there is repeated freezing and thawing. Such freezing and thawing causes the concrete to break up, to shorten the module lifetime. In addition, if one module takes on a greater amount of water than its neighboring module, that module has a tendency to ride lower in the water than its neighbors, thereby causing dock instability, particularly due to wave action. The modules can, in extreme cases, take on so much water that the freeboard of the module is lost, causing the deck of the module to be below the water surface.
While Rytand, U.S. Pat. No. 4,940,021, considers the problem of dock modules taking on water, the Rytand structure does not include concrete or other molded material in its upper portion. The Rytand buoyant wharf structure includes a lower portion with a shell surrounding a Styrofoam mass. An upper deck portion of the Rytand module is primarily wood, which has a relatively short lifetime in marine environments and has the further disadvantage of splintering which can damage the feet of barefoot pedestrians. Rytand resolves the problem of water being collected between an interface between the shell and a wale simply by providing the shell with a recess immediately below the wale. The recess has an opening located so water entering the recess flows through the opening. Such a simple solution is not applicable to buoyant wharf structures having concrete upper portions.
Rytand is also the patentee of other U.S. Patents, e.g., U.S. Pat. No. 4,887,654 and 4,709,647. Both of these Rytand patents disclose modular buoyant wharf structures having the same general construction as in the Rytand '021 patent. As such, the structures disclosed in the other Rytand patents suffer from a relatively short life because of the wooden decks thereof. The float structure of Nannig et al., U.S. Pat. No. 5,081,946, also has a wooden upper deck portion, subject to some of the same problems as Rytand devices.
Meriwether has several U.S. Patents, e.g., U.S. Pat. Nos. 4,683,833, 4,799,445, 4,974,538 and 5,199,371, all of which disclose floating docks formed of multiple floating wharf modules, each including a molded shell made of an organic compound and a wooden upper deck portion. The modules of these Meriwether patents suffer from the same problems as the wooden structures mentioned before. The structures which hold the various modules together also have durability problems. In addition, the Meriwether wharf modules have the disadvantage of having hollow shells below a water line. If a boat or other vessel contacts the hollow plastic shell, the shell is likely to break, causing the module to take on water, to substantially lower the freeboard of the entire floating dock assembly.
It is, accordingly, an object of the present invention to provide a new and improved buoyant wharf structure, a floating dock including an assemblage of buoyant wharf structures and a method of making such buoyant wharf structures.
Another object of the invention is to provide a new and improved buoyant wharf structure that is relatively easy and inexpensive to manufacture and has a long life, has long useful life, and is highly resistant to saltwater corrosion because of the way it is made and the materials from which it is made, and to provide a method of making same.
An additional object of the invention is to provide a new and improved buoyant wharf structure, particularly adapted to be used as a module for a floating deck, wherein the module has a deck made of a molded material, such as concrete, and wherein the module floats neutral, i.e., has a horizontal central axis on the wharf structure center of buoyancy.
An added object of the invention is to provide a new and improved buoyant wharf structure having a molded upper portion and a buoyant lower portion surrounded by a shell, wherein breaking of the shell has no material adverse effects on the buoyant characteristics of the structure.
A further object of the invention is to provide a new and improved buoyant wharf structure including a molded upper portion that is permanently enclosed by a mold form, including walls and a water impervious floor, wherein the floor of the mold form is maintained stable while plastic material forming the molded mass is being poured into the mold form, and to provide a method of making same.
Still a further object of the invention is to provide a new and improved buoyant wharf structure particularly adapted to be used as a module in a floating dock wherein the buoyant wharf structure is easily moved on land without damage from one place to another with a conventional industrial forklift truck.
Still an additional object of the invention is to provide a new and improved buoyant wharf structure having a molded upper portion surrounded by a permanent mold form, wherein water incident on the molded upper portion and between the molded upper portion and the permanent mold form is easily removed from the buoyant wharf structure.
Still an additional object of the invention is to provide a new and improved floating dock including multiple wharf modules which are attached to each other by a connector arrangement which assists in providing stability to the assemblage and enables the dock to have many different configurations.
A still additional object of the invention is to provide a new and improved floating dock including multiple wharf modules which are attached to each other by a structure for carrying utility lines.
A further object of the invention is to provide anew and improved buoyant wharf structure particularly adapted to receive utility lines extending to a utility tower mounted on a deck of the structure.